After all of this unfortunately LED is barely blinking. To be honest I am not an expert in electric circuits and I have no idea what is wrong with it. Can someone please give me an advice what am I doing wrong.

EDIT:

I've edited my initial circuit due to the Spehro Pefhany answer. Now the outcome is quite interesting. When I plug in jack to the mp3 player the diode is turning off. When it is not connected it is turned on.

EDIT2:

I suppose I might have just found an error. The amplifier isn't working. All the time I've been connecting my wire to the mp3 player and now I connected it to pc jack. With PC connected everything is working even without an amplifier. Even it is working better, because from amplifier I have outputs with resistors.

Now I need to check somehow my amplifier and probably get the new one. I'll update this questions when I'll know if my bet is correct.

3 Answers
3

Either the LED circuit is faulty or the audio circuit. To help you hone in on the problem I would suggest the following:

Disconnect the base of the transistor from audio+. Rewire the base pin via a 10kOhm resistor to +9V. If the LED lights, then the problem has something to do with the amplifier. If it doesn't light, then you know something is wrong with the LED driver circuit.

but I still need amplifier am I right? Or just as Brian Drummonds suggested add extra 0.5V from source?
–
sebap123Jun 11 '14 at 12:21

My comments refer to the top circuit with amplifier. The bottom one is too dependent on the source to guess whether it will work okay or not. The top one will work for sure, and can drive very high LED currents if desired.
–
Spehro PefhanyJun 11 '14 at 12:23

Add about 0.5V to it, for example with two resistors, 180K from base to +9V, and 10K from base to ground. If the audio source is DC coupled, you would also need to AC couple it (use a 100nf capacitor between base and audio input)